The present invention relates to apparatus for loading silicon wafers in magazines into furnaces or diffusion ovens and it is a general object of the invention to minimize the generation of dust particles as the loading device is inserted into the conventional process tube of the furnace from the outside.
Hitherto there have been used carriers comprising a pair of longitudinally extending supporting rods or tubes which, on insertion into the process tube by a suitable movement device, rub on the inside wall of the process tube and consequently generate dust which is detrimental to the processing of the wafers in the magazines. In an attempt at reducing the dust generation, there has been used in the industry a paddle comprising a set of rods or tubes provided with wheels along their length forming a wheeled carriage or trolley but these wheels also generate dust as they run on the bottom of the furnace tube.
In another proposal, described in Japanese laidopen Specification No. 56-36129 filed by Hitachi Ltd., a single large-diameter tube is employed as a magazine carrier, the forward or furnace end of which tube is cut away to leave a semi-cylindrical shell that is then provided with a base plate laid across the cut-out to constitute a platform for a magazine loaded with silicon wafers. This construction is massive and its thermal capacity is therefore high and due to the platform beneath the magazine, the efficiency of the flow of treatment gases around the wafers is effectively minimised. Moreover the end of the part of the tube within the furnace is provided with an outerplug of saddle-like form also filled with heat-insulating material to fit the upper part of the tube. This creates a back-pressure of gas at this point which also effectively minimises the efficiency of the gas flow around the wafers.
Apart from this, the cut-out weakens the cross-section of the tube and the large cross-section in itself impedes the gas flow.